Making a fake cast for your wrist is a great practical joke. You also might need to make a cast for a school play or a Halloween costume. Whatever the reason, with a little bit of artistic ability and know how, you can make a fake cast for your wrist that will fool anyone, except maybe a doctor.
Spread petroleum jelly on your arm and the back of your hand. This will help prevent the plaster from sticking to the small hairs and causing discomfort. If you would prefer, wear a rubber glove instead to protect your arm and skin.
Put your hand into a long white sock all the way to the toe. Carefully cut a small hole in the sock for your thumb and another bigger hole for the remaining four fingers. Slide your hand into the holes.
Cut the white gauze bandage strips into 10 and 20-inch sections. Set them aside.
Mix up the plaster of Paris in a bowl according to the package directions. Dip a 20-inch bandage strip in the plaster and wrap it gently around the sock on your arm. Do not wrap too tightly. Continue with the dipping and wrapping until the sock is covered and the cast is approximately 1/4 inch thick.
Cut the underside of the cast (where it won't be noticeable later) from one end all the way to the other. Cut slowly and carefully. Use blunt end surgical scissors to prevent cutting yourself.
Slip the cast off of your arm very carefully. This opening will allow you to put on and remove the cast whenever you want in the future.
Stuff the interior of the cast with newspapers for support. Dip the 10-inch gauze bandages into the plaster and continue to wrap the uncut portion of the cast until it is approximately 3/4 inch thick. Do not wrap plaster-laden gauze over the cast opening; keep this opening free so you can get your arm back in later. Make sure to leave the openings big enough for your thumb and fingers. Allow the cast to dry approximately 24 hours.
Remove the newspaper and the rubber glove if you used one. Put the cast over your arm. Secure the underneath portion of the cast with white duct tape so the cast will stay in place while you are wearing it. To make the cast look authentic, slide another white sock over the top of the cast. You can also wear an arm sling.
You can use pre-plastered gauze strips to make this easier. These are available in medical supply stores.